Circuit breaker panels are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload, a relatively high level short circuit, or a ground fault condition. To perform that function, circuit breaker panels include circuit breakers that typically contain a switch unit and a trip unit. The switch unit is coupled to the electrical circuitry (i.e., lines and loads) such that it can open or close the electrical path of the electrical circuitry. The switch unit includes a pair of separable contacts per phase, a pivoting contact arm per phase, an operating mechanism, and an operating handle.
In the overcurrent condition, all the pairs of separable contacts are disengaged or tripped, opening the electrical circuitry. When the overcurrent condition is no longer present, the circuit breaker can be reset such that all the pairs of separable contacts are engaged, closing the electrical circuitry.
In addition to manual overcurrent protection via the operating handle, automatic overcurrent protection is also provided via the trip unit. The trip unit, coupled to the switch unit, senses the electrical circuitry for the overcurrent condition and automatically trips the circuit breaker. When the overcurrent condition is sensed, a tripping mechanism included in the trip unit actuates the operating mechanism, thereby disengaging the first contact from the second contact for each phase. Typically, the operating handle is coupled to the operating mechanism such that when the tripping mechanism actuates the operating mechanism to separate the contacts, the operating handle also moves to a tripped position.
Switchgear and switchboard are general terms used to refer to electrical equipment including metal enclosures that house switching and interrupting devices such as fuses, circuit breakers and relays, along with associated control, instrumentation and metering devices. The enclosures also typically include devices such as bus bars, inner connections and supporting structures (referred to generally herein as “panels”) used for the distribution of electrical power. Such electrical equipment can be maintained in a building such as a factory or commercial establishment, or it can be maintained outside of such facilities and exposed to environmental weather conditions. Typically, hinge doors or covers are provided on the front of the switchgear or switchboard sections for access to the devices contained therein.
In addition to electrical distribution and the protection of circuitry from overcurrent conditions, components have been added to panels for the control of electrical power to loads connected to circuit breakers. For example, components have been used to control electrical power for lighting.
One system used for controlling electrical power to loads utilizes a remote-operated circuit breaker system. In such a system, the switch unit of the circuit breaker operates not only in response to an overcurrent condition, but also in response to a signal received from a control unit separate from the circuit breaker. The circuit breaker is specially constructed for use as a remote-operated circuit breaker, and contains a motor for actuating the switch unit.
In an exemplary remote-operated circuit breaker system, a control unit is installed on the panel and is hard-wired to the remote-operated circuit breaker through a control bus. When the switch unit of the circuit breaker is to be closed or opened, an operating current is applied to or removed from the circuit breaker motor directly by the control panel. Additional, separate conductors are provided in the bus for feedback information such as contact confirmation, etc., for each circuit breaker position in the panel. The control unit contains electronics for separately applying and removing the operating current to the circuit breakers installed in particular circuit breaker positions in the panel. The panel control unit also has electronics for checking the state of the circuit breaker, diagnostics, etc. One advantage of that system is that the individual circuit breakers can be addressed according to their positions in the panel.
A disadvantage of such a system is that the panel control unit contains complex electronics for each of the circuit breaker positions on the panel. There are typically 42 such positions. The electronics for all 42 positions is built into the switchgear whether or not circuit breakers are actually installed in all positions. For example, a customer may purchase a panel having only 6 of the 42 circuit breaker positions occupied. That customer would be required to purchase the electronics for all 42 positions, because the electronics is already contained in the single control unit.
It would be advantageous is to place the breaker control electronics in the breakers themselves, and simply send messages over a bus addressed to individual breakers. Such a decentralized control solution, however, requires a reliable addressing technique, wherein individual breakers located in specific positions on the panel may be identified and commanded. The addressing system must be robust enough to withstand the electrically noisy environment of the electrical power distribution panel.
That decentralized scenario would require that each individual breaker be identified to the control unit as being in a certain position in the panel. In one possible solution, a control unit interface prompts the customer to identify breakers with panel positions, for example, by pushing a button on a breaker when a position is prompted. That technique would place a significant burden on the customer when the breakers are installed or replaced, and relies on internal memory in the breaker to maintain reliability.
In another possible scenario, the breaker itself may read a resistance or another electronic indicator associated with a specific position in the panel. For example, a resistor may be placed on the control bus at each breaker position. The breaker would read the resistance and identify itself to the controller as being in a particular position corresponding to that resistance. That technique would require the expense of indicators at every panel position, and electronics in the breaker to perform the initialization routine.
Special panel boards and enclosures are typically utilized for systems permitting remote operation of circuit breakers. Specifically, panels are extended in length in order to accommodate a control unit. For example, a special panel may be constructed having an end that is extended to fit the panel control unit. Such a design precludes retrofitting standard panels and enclosures for use with remote-operated circuit breakers.
There is therefore presently a need to provide an improved method and system for selectively distributing power from a power distribution panel. The method and system must be robust enough to withstand the high ambient noise levels inherent in power distribution systems, and must be highly reliable. Unnecessary cost should be minimized, especially when breaker positions are left open in the panel. The physical panel layout should be such that existing non-remote actuated panel designs can be retrofitted with the necessary components.